1. Field of the Invention
The present invention relates to a remote engine control system for vehicles.
2. Description of the Related Art
Remote engine control systems are currently available that allow a user to remotely control and start an engine of a vehicle by operating a portable controller. Particularly, a user can, for example, remotely start a vehicle to warm up the engine, or remotely start the air conditioner or the audio system on the vehicle. To remotely control the vehicle, a signal is transmitted from the portable controller to the vehicle. To lengthen a transmission distance of a signal, for example, Japanese Patent Application Laid-open No. 2001-214840 and Japanese Patent Application Laid-open No. 2002-112354 teaches to use a relay unit or a relay device.
On the other hand, keys capable of short-distance radio communication are widely used that can electrically lock and unlock vehicles and facilitate locking and unlocking operation of vehicles. Such a key is called “remote key” or “radio key” (hereinafter, “remote key”). A technology has already been in practical use in which the engine of a vehicle is remotely controlled by signals from such a remote key without use of a dedicated operation terminal.
A remote key is originally use to control locking and unlocking of a vehicle or issuing an alarm (i.e., a panic alarm) for an area around the vehicle. Therefore, operation different from that for controlling locking and unlocking of a vehicle is required as a command operation for remotely starting the engine. Such operation could include pressing the button for locking the door repeatedly three times.
However, if the distance between the remote key and the vehicle is short, both the signals, i.e., the signal from the remote key and the signal relayed by the relay unit or the relay device, reach the vehicle.
In this case, a combination of the signals from the remote key and the relay terminal or the relay device may be recognized as a command (control signal) different from a command originally intended by the user for, for example, remotely controlling (starting) the engine. As a result, an erroneous command may be executed.